Calculate ASME B31.5 refrigeration piping hydrotest and pneumatic leak test pressure and hoop stress check. Use the allowable stress calculators to calculate the yield stress from the design temperature.
The test pressure should be 1.5 times the design pressure for hydrotest, or 1.1 times the design pressure for pneumatic test. Hydrotest should be used for secondary cooling piping only. Hydrotest should not be used for refrigeration piping.
Hoop stress can be calculated for either the minimum wall thickness (nominal wall thickness minus fabrication allowance), or the pressure design wall thickness (minimum wall thickness minus the corrosion allowance). Minimum wall thickness is recommended for new piping, or piping in as new condition. The pressure design wall thickness is recommended for corroded piping. The hoop stress should be ≤ 90% of yield for hydrotest or pneumatic tests.
For piping systems with combined internal and external pressure during operation, the test pressure should be calculated from the internal pressure only. The hoop stress should be calculated separately from the pressure difference during testing (use the hoop stress calculator). Use the workbook ASME B31.5 data tables to look up allowable stress data.
Reference : ANSI/ASME B31.5 : Refrigeration Piping And Heat Transfer Components (2013)
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